As semiconductor devices become more highly integrated, there is an increased demand for capacitors that provide higher amounts of capacitance per unit area. The capacitance of a capacitor may be proportional to a surface area of an electrode thereof and to a dielectric constant of a dielectric film included in the capacitor, and may be inversely proportional to an equivalent oxide thickness of the dielectric film. Thus, the capacitance of a capacitor can be increased by, for example, forming a three dimensional electrode to increase a surface area thereof, decreasing an equivalent oxide thickness of the dielectric film of the capacitor, or using a dielectric film that has a high dielectric constant.
The electrode surface area can be increased by increasing a height of a bottom electrode (or a storage electrode) of the capacitor, by increasing an effective surface area of the bottom electrode (for example, using a hemi-spherical grain), or by forming a cylindrical bottom electrode that has inner and outer side surfaces that both contribute to the surface area of the electrode. A dielectric material having a high dielectric constant, such as metal oxides (e.g., TiO2 and Ta2O5) or Perovskite ferroelectric materials (e.g., PZT (PbZrTiO3) or BST (BaSrTiO3)), may be used as the dielectric film of the capacitor.